In case you don't know, proofreaders don't just read and mark mistakes. You have to have the writing skills to be able to correct the mistakes even in syntax. Another thing that makes it different from just reading is that you have to be to always be able to find the mistakes. It is a natural thing that when you read, you automatically correct what you read in your mind, and only a skilled proofreader can over come that and actually find the mistakes while reading very quickly.
Did you find the mistakes in what I just wrote above as soon as you read them? Here it is again with the corrections..
Proofreaders don't just read and mark mistakes. They have to have the writing skills to be able to correct even mistakes in syntax. Another thing that makes proofreading different from ordinary reading is that one must always find the mistakes. It is a natural thing that when one reads, the mind automatically corrects what is read. A skilled proofreader must overcome that natural inclination and find mistakes while reading very quickly.